Microwave enhanced synthesis of N-propargyl derivatives of imidazole: A green approach for the preparation of fungicidal compounds

N-Propargyl imidazole has been synthesized by Knoevenagel condensation of benzaldehyde with propargyl bromide, assisted by microwave irradiation. Two alkaline-promoted clays (Li⁺- and Cs⁺-exchanged saponites) have been used as catalysts. The influence of several factors, such as irradiation power, irradiation time and alkaline promoter has been studied. The catalysts were characterized by XRD and chemical analysis. The basicity enhancement is directly connected to the presence of alkaline metal promoters in the saponite structure. In addition, a significant increase in the conversion values has been found when the reaction is activated by microwave irradiation, as compared with thermal activation. The yield to the N-propargyl imidazole shows a maximum for the Cs⁺-saponite at 750 W in only 5 min of microwave irradiation. This green and solvent-free procedure can be extended to the preparation of other N-substituted heterocycles, which could serve as precursors in the primary route to pharmaceutical compounds of interest.     

Increase in the light collection from a scintillation strip with a hole for the WLS fiber using filling materials of various types

The light collection of extruded scintillation strip samples with the help of WLS fibers placed in a longitudinal hole inside of the plates has been measured. The holes are filled with various liquid fillers. Measurements are performed under irradiation by cosmic muons. A method for pumping a liquid filler with a viscosity of more than 10 Pa s into the strip hole with a WLS fiber inside is devised and successfully tested.     

Stability of biomimetic ferrofluids established by a systematic study using microwave irradiation at defined wattages

An established biomimetic process for the synthesis of aqueous ferrofluids using polymers has been subjected to systematic microwave irradiation at different wattages primarily to see if the magnetization could be increased by microwave irradiation and if so how would it affect the stability of the fluid. Care has been taken to maintain ambient conditions of synthesis even after three cycles of microwave irradiation before oxidation and ten cycles after it, so as not to violate the basic principles of the process. Detailed characterization using, x-ray diffractometry, transmission electron microscopy, fourier transform infra-red spectroscopy, dynamic light scattering, thermo-gravimetric analysis, differential thermal analysis and vibrating sample magnetometry showed that these fluids containing iron oxide nanoparticles-poly(vinyl) alcohol nanocomposites are highly stable in the proportions established by us. Measurements at five different wattages double the saturation magnetization but the stability remains unaffected compared to the one without microwave irradiation, forcing us to believe that the incubation of the iron salt solution and the polymer in the right proportion before oxidation is what contributes to the stability and that increasing the number of cycles of microwave irradiation at this stage, perhaps, would have led to a more pronounced effect.     

The Effect of Microwave Irradiation on the Crystallization Behavior of PET/PEN Blends

The crystallization behavior of poly(ethylene terephthalate) (PET)/poly(ethylene‐ 2,6‐naphthalate) (PEN) blends before and after microwave irradiation for different time intervals has been investigated by means of wide angle X‐ray diffraction (WAXD) and differential scanning calorimetry (DSC) techniques. It was found that microwave irradiation could greatly affect the crystallization behavior of PET/PEN blends and significantly enhance their degree of crystallinity. For the PET/PEN (90/10) blends, the degree of crystallinity increased from 15 to 45%; for the PET/PEN (60/40) blends, the degree of crystallinity significantly increased, from 1 to 36%. However, with increasing irradiation time, the degree of crystallinity didn't continually increase. It reached a maximum at certain time point. The cold crystallization enthalpy △Hcc gradually decreased as microwave irradiation time increased and the melting enthalpy △Hm vis‐à‐vis the long time interval of such irradiation was decreased. In addition, the mechanism for microwave irradiation affecting the crystallization behavior of polymers is discussed.     

Manifestations of incompressible strips in the edge magnetoplasmon spectrum in the quantum Hall effect regime

The behavior of the main edge magnetoplasmon mode in the quantum Hall effect (QHE) regime has been analyzed by the method of optical detection of resonance microwave absorption. Near a filling factor of 2 at a temperature of about 0.3 K, the main edge mode splits into two modes seemingly due to broadening of the incompressible strip at the edge of the two-dimensional electron gas under such conditions.     

微波辐照对胶原蛋白三股螺旋结构的影响

胶原蛋白的三股螺旋结构是其不同于其他蛋白质的特殊结构，也是其具有特殊功能的基础，然而，胶原的三股螺旋结构易在外界条件的影响下被破坏。目前微波已被越来越多的应用于胶原蛋白的提取和改性过程，但是关于微波辐照对胶原蛋白结构影响的研究还相对较少。首先从牛跟腱中提取胶原蛋白，然后采用0.5 mg·mL-1的胶原蛋白溶液在30 ℃下以微波辐照保温为实验样，水浴加热和未经加热处理为对比样，最后采用紫外-可见光谱、傅里叶变换红外光谱、圆二色谱以及荧光发射光谱等方法，对不同加热方法中胶原蛋白的三股螺旋结构和超分子结构进行表征，研究了微波辐照对胶原蛋白结构的影响。实验结果表明，在低于胶原变性温度的条件下，无论是微波辐照还是水浴加热都不会破坏胶原蛋白的三股螺旋结构，也不会使胶原蛋白变性。但是，与水浴加热相比，微波辐照会对胶原蛋白的聚集行为产生抑制作用。微波辐照对胶原蛋白的作用既有与常规加热相同的热效应，又有常规加热过程中不存在的非热效应，非热效应表现为抑制胶原蛋白的聚集行为。研究结果可为微波场中胶原蛋白结构和性质的变化提供科学依据。     

Microwave annealing of defects in ferroelectric triglycine sulfate

The effect of microwave irradiation of ferroelectric triglycine sulfate (TGS) samples with different degrees of imperfection (determined by the annealing conditions) has been investigated. It is shown that the irradiation effect depends on both the degree of perfection of the samples and the irradiation time (dose). As for gamma irradiation, low doses of microwave radiation lead to partial annealing of defects and, therefore, should improve the parameters of TGS-based devices. High irradiation doses cause degradation of TGS properties, which is highest in perfect crystals.     

非对称条形纳磁体的铁磁共振频率和自旋波模式

通过建立微波激励下的非对称条形多铁纳磁体的微磁模型,研究了倾斜角和缺陷角对该形纳磁体的铁磁共振谱和自旋波模式的影响.通过对微磁仿真得到的动态磁化数据进行分析发现,非对称条形纳磁体倾斜角度增加,铁磁共振频率随之增加,而这一现象与纳磁体的缺陷角度无关.倾斜角不变,非对称条形纳磁体的铁磁共振频率与缺陷角度呈单调递增关系,并且不同缺陷角度纳磁体的自旋波模式显示出极大的差异.非对称条形纳磁体与矩形纳磁体相比,它的自旋波模式局部化,具体为非对称条形纳磁体的自旋波模式不对称且高进动区域存在于边缘,表现为非对称边缘模式.倾斜角改变导致纳磁体内部退磁场变化,引起纳磁体边缘模式的移动,而中心模式对倾斜角的变化并不敏感.最后,对建立的模型在高频微波磁场激励下的磁损耗进行了分析,验证了模型的可靠性.这些结论说明缺陷角和倾斜角可用于纳磁体自旋波模式和铁磁共振频率的调谐,所得结果为可调纳磁微波器件的设计提供了重要的理论依据和思路.     

A study on beam profile of an industrial electron accelerator

Experimental evaluation of electron beam profile of a recently upgraded industrial electron accelerator has been carried out to study characteristics of the beam required for the irradiation of various industrial products. Calibrated cellulose triacetate (CTA) film strip dosimeters were used for the measurement of dose profile along and transverse to the scanning direction at different distances in air under the beam extraction window in dynamic (conveyor) and static mode of operation. Two-dimensional dose distribution mapping under the beam has also been measured by using a large number of CTA strip dosimeters. The obtained result shows that the electron beam emerging out from scanning horn has a good uniformity along the scanning direction within 90% of the average maximum dose. Also, the paper reports depth dose distribution in unit density material under the 4.5?MeV beam. Using this study, area affecting dose to the product is controlled within the limit for the irradiation.     

On the Cutoff Wavelength of Rectangular-Shaped Microshield Line by Edge Element Method

In this paper, the cutoff characteristic of rectangular-shaped microshield transmission line has been analysed by edge element method. Dependence of cutoff wavelengths on the thickness of metallic signal strip, dielectric constant of dielectric substrate and the width of the rectangular-shaped ground conductor are presented in tabular form. Numerical results in this paper have important values in design of rectangular-shaped microshield lines in microwave and millimeter wave integrated circuits.     

Microwave Photoresistance of a Two-Dimensional Topological Insulator in a HgTe Quantum Well

JETP Letters - The microwave photoresistance of a two-dimensional topological insulator in a HgTe quantum well with an inverted spectrum has been experimentally studied under irradiation at...     

Microwave photoconductivity of bifacial silicon solar cells of <Emphasis Type="Italic">p</Emphasis><Superscript>+</Superscript><Emphasis Type="Italic">nn</Emphasis><Superscript>+</Superscript> type under laser irradiation

The microwave photoconductivity of silicon solar cells under laser irradiation has been investigated. It is shown that shunting of the solar cell region exposed to light by the rest of the cell may reduce significantly the relaxation time of microwave photoconductivity in comparison with the nonequilibrium charge carrier lifetime in the base region.     

Tc enhancement!

The equilibrium critical temperature of a superconducting aluminum strip has been determined with three different methods. The results agree to within 1 mK. By applying microwave radiation superconductivity was maintained up to 57 mK above this critical temperature. These data clearly establish the existense of T_c enhancement.     

微波辐照对无线电引信的影响与作用机理

 选择某型集成电路无线电近炸引信,从勤务处理状态和工作状态两方面,研究了无线电引信的微波辐照效应,确定了被试无线电引信的微波辐照损伤阈值范围在140~150 kW/cm²之间,误炸阈值在100 kW/cm²左右。微波辐照通过前门耦合导致无线电引信的高频振荡管和低频组件产生硬损伤,通过直接作用于起爆执行电路使处于工作状态的无线电引信出现误炸。     

微波辐照对无线电引信的影响与作用机理

选择某型集成电路无线电近炸引信,从勤务处理状态和工作状态两方面,研究了无线电引信的微波辐照效应,确定了被试无线电引信的微波辐照损伤阈值范围在140~150 kW/cm2之间,误炸阈值在100 kW/cm2左右。微波辐照通过前门耦合导致无线电引信的高频振荡管和低频组件产生硬损伤,通过直接作用于起爆执行电路使处于工作状态的无线电引信出现误炸。     

THE SUPERCONDUCTING TUNNELLING CURRENT UNDER MICROWAVE IRRADIATION

In this article, the non-eguilibrium Green's function method developed by Keldysh^[1]and Larkin-Ovchinnikov^[2]is used to derive the expressions for quasi-particle and Josephson current of a superconducting junction under microwave irradiation. As an example, the results up to second order of irradiation field have been calculated. The influences of the microwave have been discussed briefly.     

Family of graphene-based superconducting devices

A family of highly sensitive devices based on a graphene nanobridge and superconducting electrodes has been developed, manufactured, and examined. These devices can be used to create a graphene-based integral receiver. A cold-electron bolometer prototype with superconductor-insulator-normal metal tunnel junctions has been studied. Its response to a change in the temperature and external microwave radiation has been measured. A superconducting quantum interferometer with a graphene strip as a weak coupling between superconducting electrodes has been examined. The corresponding modulation of the voltage by a magnetic field at a given current has been measured. The effect of the gate voltage on the resistance of graphene has been analyzed for these samples. To confirm that graphene is single-layer, measurements with the reference samples were performed in high magnetic fields, displaying the half-integer quantum Hall effect.     

The impedance-characteristic method in the study of specific temperature features of dielectric anomaly suppression in triglycine sulfate

The reflection and absorption coefficients in a waveguide loaded on ferroelectric triglycine sulfate (TGS), which has a layered domain structure near the phase transition, are calculated by the impedance-characteristic method. The calculated and experimental data do not reveal any correlations with the specific temperature features in the TGS dielectric response to microwave irradiation. The mechanism of the microwave effect is discussed.     

Spectra of Two-Dimensional “Proximity” Plasmons Measured by the Standing-Wave Method

JETP Letters - Plasma excitations in a two-dimensional electron system partially screened by a metal strip gate are investigated using the optical detection of resonance microwave absorption. The...     

Microwave absorption in high-Tc superconductors studied by the EPR method

Dependences of the microwave absorption on temperature, magnetic field and microwave power obtained for the high-T _c superconductors are presented. Shape of the magnetically modulated microwave absorption, low-field phase diagram and overheating of the Josephson junction system induced by microwave irradiation are discussed. The model of the Josephson junction system interacting with microwaves has been used to explain the behavior of the high-T _c superconductors in low magnetic field.